This invention relates to implantable devices for promoting tissue growth or tissue expansion, and more particularly to a flexible, foldable needle stop device for a fluid expandable prosthesis.
Tissue expander prostheses are generally used to promote tissue growth by gradually expanding the prosthesis beneath the skin in an area where tissue growth is desired. The prosthesis is typically a collapsible shell formed of a flexible, foldable material which establishes a fluid chamber. Infusion of fluid in the fluid chamber expands the prosthesis to promote tissue growth.
Infusion of fluid into a tissue expander prosthesis is normally accomplished with an infusion needle. Since a tissue expander shell is likely to leak if punctured by a needle, it is common practice to use a tissue expander system that includes resealable septums such as shown in U.S. Pat. Nos. 4,190,040; 4,463,733; and 4,543,088.
Septums are relatively inflexible, non-expandable, infusible hollow structures that enable fluid to flow into a tissue expander structure once the inner capacity of the septum is filled. As shown in the foregoing patents, the septum is connected to a tissue expander structure by a conduit such that fluid infused into the septum is directed by the conduit into the tissue expander chamber. Septums usually have the capability of being resealable when an injection needle is withdrawn.
Known tissue expansion systems often require implantation of a septum, a tissue expander prosthesis and the conduit that connects the septum to the tissue expander prosthesis. The surgery for implanting a tissue expansion system normally includes an incision or incisions through which the implant is directed and a surgical pocket for accommodating the implant. The size of the implantation incision and pocket is generally based upon the size of the respective components of the tissue expander system.
In an attempt to simplify tissue expansion systems and reduce the size of implantation incisions and surgical pockets, a self-sealing tissue expander device has been developed and is the subject of a co-pending patent application. The self-sealing tissue expander device eliminates the need for a septum and the connection tube that normally connects the septum to the tissue expander. As a result, the implantation incision and the surgical pocket needed for implanting the self-sealing tissue expander need only be of sufficient size to accommodate the tissue expander, since there is no accompanying septum and connection tube.
When a self sealing tissue expander of the type previously referred to is used without a septum, it is desirable to provide a needle stop device therein. Needle stop devices are usually rigid, impenetrable structures that resist needle penetration and block further passage of a needle beyond the location of the needle stop. The needle stop device prevents an infusion needle that has entered the infusion chamber of the tissue expander device from passing beyond the chamber through the tissue expander shell. The needle stop device ideally is of a size and shape which does not obstruct entry of a needle into the fluid chamber but is of sufficient size to prevent through passage of the needle beyond the chamber.
Implantation of a tissue expander prosthesis is normally carried out with the prosthesis in an unexpanded or substantially empty condition, wherein the shell can be folded or otherwise compacted to the smallest practical size to minimize the incision needed to accomplish implantation. However, in tissue expander devices which include needle stops, the smallest practical compaction of the tissue expander is usually determined by the size of the relatively rigid needle stop device. Therefore, the minimum size of the implantation incision often corresponds to the size of the needle stop device.
It is thus desirable to provide a flexible, foldable needle stop structure for a tissue expansion device that enables the tissue expansion structure, along with the needle stop structure to be folded or otherwise reduced in size for implantation through an incision of minimal size.